Mark Neate, director of environment, safety and security with Sellafield Ltd, has told employees: "We will minimise attendance at all of our sites and wherever possible everyone should continue (or start) working from home.

"We will maximise social distancing and the support we can provide to our community.

"We will continuously review our decisions and communicate these to you as quickly as we possibly can.

"We will continue to implement government advice – in some cases we will go further to protect the long-term safety and security of our site."

He said Sellafield's focus is on making sure its staff and communities are safe and that nuclear safety is never compromised.

"I understand that this is a challenging time for everyone and that many of us are balancing complicated personal circumstances with our commitment to nuclear safety and our business. I thank you for your continued support, patience and flexibility.

"The coronavirus pandemic demands an unprecedented response from all of us. We will always be responsible and conservative in our decision making and our priorities remain the protection of our workforce and the maintenance of safe and secure site operations.

"Last week we made an operational decision to undertake a controlled shutdown of our complex operational facilities. The process of controlled shutdown is still underway. As we now accelerate the shutdown, we acknowledge that we still have a critically important national mission to undertake and that any decision we make now could impact our ability to deliver in the future – for our workforce, communities, business and country."

Immediate actions from Monday March 23:

"From Monday we are directing that you do not attend your place of work unless you have a role with a responsibility for maintaining nuclear safety and security.

"We will be restricting access to all of our satellite offices. If you are not sure whether your role directly impacts nuclear safety or security please contact your line manager for guidance.

"We will also be temporarily pausing any project and supply chain work that does not directly impact nuclear safety and security. This will help us to maximise social distancing in all of our workplaces.

"During the next week we will review our project work and decide which projects must continue and how we can do that.

"This reduced attendance therefore also applies to our supply chain colleagues and we ask that those colleagues contact their employer if any clarification is needed. To be absolutely clear, suppliers are not to attend site from tomorrow whilst we carry out our review."

The company said Mitie employees in the civil guard force and Mitie One FM employees should attend as normal. They will be contacted by their line manager if they are not required. Cavendish Radiometric are also required to attend.

"Those not attending (unless ill or care giving) are expected to undertake work from home as directed by line management," said Mr Neate. "We recognise this is not possible for everyone and that arrangements to do so may not yet be in place. All employees and suppliers are asked to maintain regular contact with their line management to confirm working arrangements as we expect these to change over time.

"During this period of uncertainty we may require you to attend work to carry out specific tasks. We thank you for your continued professionalism, flexibility and commitment to our business."

He add that the company expects to play a more significant role in supporting the community."You may be asked to carry out a different role or contribute to a different area of the business. We are also starting to identify areas within our community where we can provide support and may ask you to assist with this.

"There will be more guidance and advice published supporting these new arrangements, especially regarding the use of technology, please bear with us while this guidance is being developed, your patience is appreciated.

"For those working in our active facilities new arrangements are in place for entering and exiting our controlled areas. Please look out for these on your return."